Various dental handpieces are known in the dental art. Turbine driven handpieces are widely used by dentists. Dental handpieces include a handle and drive head for supporting the rotating components dental bur. A connector, e.g., a swivel connector, connects the handpiece to various air, water, light and power supply conduits, generally combined in a singular flexible cord. The drive head houses a dental bur drive arrangement that is typically composed of a dental bur-retaining mount or chuck, and a motor or turbine rotatably mounted in the head for driving the chuck. The chuck holds the dental bur for rotation.
The dental bur is removable from the chuck and interchangeable with other dental burs for providing various sizes and dental operations. In known handpieces, the dental bur is maintained by the chuck against axial and radial movement and slippage in the drive arrangement. Screw lock or pushbutton lock arrangements may be provided for the manual locking and releasing of the dental bur in and from the chuck.
Manufacturers of dental handpieces have increased the power wattage that may be output from a dental handpiece. The higher power of the dental handpiece may reduce the percentage of the total power that is delivered to the dental bur. Bur slippage may occur in the chuck during heavy cutting operations, resulting in loss of control of the operation, chatter of the bur during cutting operations, and loss of precision that is essential in dental operations. Slippage of the bur may cause the chuck to wear grooves on the bur shank, causing interference between the bur and the chuck and making removal of the bur from the chuck difficult. Also, unsafe patient conditions may occur due to burs “walking out” of the chuck, i.e., displacing the bur axially out of the chuck due to wear in the chuck.
Further, high frequency or ultrasonic vibrations may cause welding of the bur shank to the chuck. Such unintentional welding requires very high axial applied force to a push button type chuck to release the bur, and may result in chuck or turbine damage, and may require removal of the bur using pliers or forceps.
Prior art chucks of dental handpieces are almost exclusively designed to hold the dental bur by way of friction fit only. Examples of such constructions are found in U.S. Pat. No. 3,869,796, U.S. Pat. No. 4,595,363, U.S. Pat. No. 5,275,558, and U.S. Pat. No. 5,549,474. Only low torque transmission is possible between the chuck and the bur in such constructions, high torque leading to slippage of the bur. At the high rotational speeds achieved and high torque achieved by modern dental handpieces, bur slippage, in both the axial and rotational directions, can become a problem. Rapid deceleration of the bur can also lead to rotational slippage, for example, when the drive continues to rotate while the bur is locked or snagged. Friction between the drive assembly and the dental bur during rotation leads to significant wear of both elements overtime. Friction heat can cause permanent damage to the drive spindle components, especially the flexible friction arms of the chuck, which are normally made of heat tempered material. The damage can lead to rotational slippage and even axial slippage of the dental bur, possibly resulting in an accidental release of the dental bur from the handpiece. Accidental release of a dental bur during high speed rotation can pose a threat to both the patient and the dentist. Continued wear of the bur and drive assembly during operation necessitates routine maintenance and repair of expensive handpiece components.
Thus, a dental handpiece and rotary dental instrument system is desired that reduces slippage and walk out while providing complete power and torque transfer from the dental handpiece and rotary dental instrument and increasing cutting efficiency.
Intended advantages of the disclosed systems and/or methods satisfy one or more of these needs or provide other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments that fall within the scope of the claims, regardless of whether they accomplish one or more of the aforementioned needs.